One thing to remind everyone who has sent in a PMQ answer. You will immediately receive an automated reply; this is done so that you know that your email has been received and not to send another one! Also, when you see this, please add the domain to your white list so that the prize winners announcement doesn't get caught in whatever spam trap you may have.
OK, without any further rambling...
Jeffrey Bond from the USA
These were the only two entries that had at least one of the questions correct. If you wish to try the question, then just go to PMQ16 - but be careful as the answers are in the comments section!
Chris Breederveld from The Netherlands
Tan Qi Huan from Malaysia
You can try the question at PMQ17. Be careful, the most common mistake in this puzzle was to forget that there is an even prime!
Congratulations to all the winners and thanks to everyone who participated.
If any of the above winners wishes to add a link to their personal page such as G+ or Facebook, then please get in touch or send me a PM within G+. Thanks.